Insects in the City

Tuesday, May 12, 2020

The large yellow-orange head and dark eyes and dark thorax
distinguish the Asian giant hornet from similar large wasps.
Photo courtesy Washington State Department of Agriculture.

If ever there was an insect pest designed to generate fear and panic, it would be the Asian giant hornet, Vespula mandarinia. The largest wasp in the world, with a sting once described like a hot nail being punched through the skin, we should give this wasp credit. It is one scary dude (or more accurately dude-ess).

Adding to the hornet's fearsome reputation is it's impact on honey bees. One of the favored foods for the Asian giant hornet is the brood and workers of social wasps and bees, including honey bees. In the fall hornets start actively searching for bee and wasp nests. Once a nest is discovered, the hornets overpower the inhabitants, bite off their heads and consume the brood and honey [in the case of honey bees].

Commercial honey bee apiaries are especially vulnerable to hornet attack because of the close spacing of hives. An apiary can quickly turn into a scene of pillage and destruction as wasps move from hive to hive.

So that's the essence of the bad news that you can read in most media accounts of the hornet. Here are a few things every PMP should know about this hornet as you talk with your customers.

Background

The largest wasp in the world, the Asian giant hornet is
1 to 1 ½ inches long with a ¼ inch-long stinger. Photo
courtesy Washington State Department of Agriculture.

The Asian giant hornet was first detected in September, 2019 on Vancouver Island in British Columbia, about 200 miles northwest of Seattle, WA. In December, three months later, a dead wasp was found in the small town of Blaine, Washington (100 miles north of Seattle) and reported to the Washington Department of Agriculture. It was confirmed as the first detection of Vespa mandarinia in the U.S. As of last February according to the USDA, so far a total of six sightings have been confirmed from British Columbia and Washington State (September through December).

You need to know. So far this wasp is only found in Washington State and British Columbia. There is practically zero chance that anyone outside northwest Washington and southern BC will encounter this wasp this year. Most of your experience with this wasp will be explaining to customers why they are not the first house in their state to get Asian giant hornets, aka "murder hornets" (more on identification tips below).

Researchers are still unsure how the Asian giant hornet made its way to North America, but suspect that mated, overwintering queens may have been transported in soil-containing plant pots shipped from Asia. A similar route of entry was responsible for introducing another Asian hornet to France a few years ago. Recent genetic analyses suggest that the wasp was introduced on at least two occasions very recently.

You need to know. Human transport of the wasp has occurred but it is likely a rare event. It is more difficult to transport a social insect, because it must be transported either as a mated queen or as an intact colony. Individual hornet workers do not survive long if separated from their colony. In my opinion, this means that, given reasonable precautions, we shouldn't expect rapid spread of this wasp throughout the states. On the other hand, it is estimated that the wasps would be capable of surviving in plant hardiness zones 6 and above, which means that about 2/3 of the U.S. may ultimately be capable of supporting this hornet.

Activity

Like our smaller, ground-nesting yellowjacket wasps, Asian giant hornets build underground nests that survive for one growing season. Queens leave the nest with the coming of cold weather and overwinter in protected hiding places until mid-spring when they emerge and hunt by themselves. Small colonies are formed and by early- to mid-summer worker wasps are produced and cooperative nest building proceeds. Not until fall do these wasps go on their campaigns of slaughter and occupation of bee hives.

You need to know. Most people will face little risk of stings from Asian giant hornets. These insects are aggressively territorial only when their nest is disturbed. Nests are usually found in wooded areas and only occupied by guard hornets from mid-summer through the fall. If their biology turns out to be similar to our native yellowjacket wasps, most nest encounters (and stings) will occur after the nest grows in size in late summer and fall (September and October). There is a more limited time frame in the fall (October and November) when honey bee hives are at risk from attack by wasps. Fall will be the time to be most concerned about stings and beehive attacks from these wasps.

Identification

This may be the most useful information in this post, as most of a PMP's role will be reassuring the public that any big insects they see are NOT Asian giant hornets.

The closest relative of the Asian giant hornet is Vespa crabro, the European giant hornet. In the south and west, cicada killer wasps are the most common giant hornet look-alikes, reaching up to 1 ½ inches in length, but are generally more slender and lacking the large yellow-orange head and contrasting black eyes.

You need to know. There are lots of big insects that people will mistake for Asian giant hornets. The chance of encountering one of these invasive hornets outside of Washington state is about zero right now. But be ready to put a name on the insects your customers will bring to you.

Hornet vs. Wasp

In this post I've used the terms hornet and wasp almost interchangeably. That is because hornets are a kind of wasp. The term wasp refers generally to any member of the insect order Hymenoptera that is not a bee or an ant. Most of the stinging wasps we think of as pests belong to the wasp family Vespidae. The term hornet refers to vespid wasps in the genus Vespa. In the U.S. we have only two species of hornet, the European giant hornet and (now) the Asian giant hornet. Despite its common name, the baldfaced hornet in the genus Dolichovespula is considered a type of yellowjacket wasp, so is not technically a hornet.

You need to know. There are only two true hornets in the U.S., however, the smaller yellowjacket wasps and Polistes paper wasps are also social and will aggressively defend their nests like hornets and some bees. Any of these species can be considered pests when their nests are built in areas where people travel or live.

Control

Japanese hornet-hunters wear special protective gear to excavate a nest. These special suits are designed to be slippery so the hornet cannot hold on; and are made of tough fabric that keeps stingers from penetrating. Note the use of smoke to calm the hornets while removing brood for human consumption. Photo credit Nonaka, 2008. From USDA APHIS 2020.

A variety of approaches have been taken to control the Asian giant hornet, but none seem capable of eradicating the pest at this time. The USDA APHIS recently published response guidelines for the Asian giant hornet which includes a summary of different control measures with pros and cons of their use. Pest management professionals who encounter this hornet should be aware that traditional bee protective suits are not adequate protection for the one-quarter inch stingers carried by this hornet. In Japan special suits are sold ($700-$900) to protect people exterminating or digging up hornet colonies for food.

You need to know. Killing individual wasps through baits or sprays will not control this species. Locating and exterminating the nest is what is being attempted in Washington state right now. Anyone who encounters a suspected Asian giant hornet should contact their state department of agriculture or a university entomologist. Do not attempt to remove or kill a suspected Asian giant hornet nest without adequate personal protective equipment.

Monday, April 20, 2020

Kudzu bug has a unique ovoid shape. The wings
are hidden under a shield-like scutellum, makingit look more like a beetle than a true bug. Photo by Dan Suiter, University of Georgia.

In October 2009, millions of small, pill-like bugs startled homeowners across nine counties in northeast Georgia. The never-before-seen insects covered the sides of homes by the thousands, and concerned citizens began calling Extension offices daily. Though puzzled at first, entomologists eventually identified the insect as "kudzu bug", an exotic insect never before seen in the U.S.

The kudzu bug, Megacopta cribraria, is native to Asia, where it is widely distributed. As its name implies, its preferred host plant is the invasive weed, kudzu. No one knows how it got here, but like many invasive pests it made itself at home quickly. Highly mobile, within a year the kudzu bug had spread to 60 north and central Georgia counties. Two years later every county in the state had them.

Last week Texas became the 14th state with verified populations of kudzu bug. Sharp-eyed county Extension agent Kim Benton reported kudzu bugs from a home garden in Rusk, TX, south of Tyler. The bugs were clustered on eggplant and other vegetables before being transplanted into the garden.

Description and damage

It is hard to mistake kudzu bug for anything else. The bug is beetle-like in appearance with a unique, four-sided, ovoid shape. It is greenish-brown and shiny, up to 1/4 inch-long (3.5-6 mm). It uses its piercing/sucking mouthparts to feeding on the sap of kudzu and other legumes.

For soybean farmers and vegetable growers kudzu bug is another pest to battle. The bugs overwinter close to kudzu, their favorite food in the spring. But in summer they move into soybeans where they can cause significant yield reductions. To a lesser extent they feed and reproduce on sweet peas, snap beans, cowpeas, lima beans and wisteria. It may be seen on other plants as well, where it gathers temporarily, usually to move on in a day or so.

Is it a good bug?

Anyone familiar with the weed kudzu will be excused for thinking that having kudzu bug might be a good thing. After all, one of the reasons kudzu is such a horrible weed is that few things eat it. Wouldn't it be good to have an insect to keep kudzu in its place?

That's what the good folks in Georgia hoped. But according to Georgia extension entomologist Phillip Roberts, their optimism didn't last. "The first years we saw what we thought was a lessening of the kudzu problem. Other weeds seemed to be competing more effectively with the kudzu." But after a year, he said, the kudzu seemed unfazed. "There has not been any noticeable decline in kudzu growth since the beetle moved in."

A (minor) crossover pest

Kudzu bugs cover the eave of a home in Georgia. Photo by
Dan Suiter.

Kudzu bug is one of very few agricultural pests that are structural pests as well. Problems in Georgia with kudzu bug are mostly restricted to homes near kudzu patches and soybean fields (rare) in Texas. According to Georgia extension entomologist Dan Suiter, unlike the multicolored Asian lady beetle, kudzu bugs are attracted to buildings in the fall but rarely come indoors. "We never really see them getting inside," he said.

Nevertheless, expect that some homeowners will be upset over thousands of bugs clustering on the outside of their homes, especially on white-painted gutters, siding and around windows. Also, the bugs have an odor and secrete a staining fluid when disturbed.

Kudzu bug activity around structures is most noticeable in the fall. This is when bugs from nearby kudzu are seeking shelter and are attracted to homes.

How bad?

It's yet to be seen whether kudzu bug will become a noticeable pest in Texas, but indications from Georgia suggest it will not be a serious long-term pest. Because kudzu is less prevalent in Texas than Georgia and other southern states, the bug is likely to occur only in east Texas, and populations limited to start with. But at least two egg parasitiods (egg predators) and a fungus called Beauveria bassiana, have severely reduced the kudzu bug problem in Georgia and most southern states. After being overwhelmed with calls the first five year after the bug's discovery, today Suiter says he "doesn't see more than 20 bugs a year" brought into his office.

Vegetable gardeners in counties with kudzu may be more bothered. Edamame, peas or other beans are susceptible to these bugs and may require treatment.

Control

If you are called on to manage kudzu bugs around a home, here are a few tips:

Focus on the outside of the building when controlling kudzu bugs--few bugs will be indoors, though caulking and sealing will also help in that regard.

Pyrethroid insecticides are generally effective against kudzu bugs. Bifenthrin and lambda-cyhalothrin are especially good in crop situations, according to Roberts. Suiter said his research shows Alpine WSG (dinotefuran) also works well and has the added advantage of quickly killing the bugs, in seconds, eliminating the chance for unsightly aggregations to occur.

Look for, and treat, any crack or crevice where bugs are aggregating. Examples include: gaps behind siding and around windows and doors; high places (such as around soffits, fascia boards and gutters); even loose bark on nearby trees.

If kudzu is present outside the home, use a herbicide to remove it, preferably during the spring or summer. This can help reduce the numbers of bugs coming to the outside of the home in the fall.

If you find what you believe are kudzu bugs we would love to see a clear photo. Also save specimens to bring to your county Extension office for official confirmation. This can help us track the spread of kudzu bug within the state.

Tuesday, March 17, 2020

The strategy behind today's protective measures of hygiene, socialdistancing, and reducing human interaction is called "flatteningthe curve". This is why Extension programming is being temporarily suspended. Adapted from CDC/The Economist.

Who would have believed, even one week ago, that coronavirus would dominate our lives so quickly and severely? This sort of thing is something that happens to other countries, not ours. Yet here we are.

The reality of coronavirus hit home to me last week when we realized that we couldn't follow through with our plans to offer a long-planned mosquito control class as part of our IPM Experience House class curricula. Texas A&M AgriLife and our local campus have moved to emergency mode, effectively shutting most training classes down for the foreseeable future.

In addition to IPM House classes, upcoming school IPM coordinator training courses are similarly affected. We are cautiously considering whether we may be able to offer classes in May and June.

It took me a while to grasp the significance of the coronavirus shutdown strategy; but for what it's worth, here are a few facts and links that turned me around this week.

Yeah, it sounded bad in China, but look at Italy. In Italy, where health care systems are more similar to our own but where quarantine actions were slow to be adopted, a crisis situation developed with lightning speed in emergency rooms of afflicted areas. And if you think Italy's health care is inferior to our own, consider one statistic. In hospital beds per 1,000 people, Italy leads the US 3.2 to 2.8. Anyone thinking that our doctors and hospitals could do better in the face of overwhelming numbers of cases as in Italy would be wrong.

Thankfully, there is a strategy behind the "stay at home" message we are hearing so much about. It's called flattening the curve, and it's based on the impact that self isolation and social distancing can have on the speed of spread of COVID-19. While it may seem inevitable that some of us will get the virus, by reducing our exposure to others we can slow the rate of virus spread. And if we do this, we might be able to spare our health care system the tsunami of cases seen in Italy.

Our country rightly invests billions of dollars each year in science and health care. It's time to listen to those smart folks who have dedicated their lives and their intellects to understanding health and illness and the spread of disease. They don't know everything, of course, but they know a lot more than us non-health professionals know.

So for all these reasons, I am working this week in an empty building with plenty of social distance around me. We use hand sanitizer, wash our hands regularly and stay away from large gatherings including, unfortunately, classes where we might otherwise be training some of you.

Let us pray for our communities and our nation, and look forward to celebrating a return to face to face interactions in a matter of weeks. Be assured that our IPM training classes will resume as soon as possible.

I love my job--especially when I get to identify tiny insects that no one else wants to look at. I recently received an insect from a gentleman whose daughter had been bitten at home. I could tell immediately we were dealing with a flea--usually a routine identification to confirm that the tiny insect was a cat flea. But this specimen was different, and prompted a closer look. What fun!

Before I let the "cat flea" out of the bag, one of the fleas below was the flea I saw this week. Can you identify which is the one that was not a cat flea? (Hint: it doesn't have anything to do with the color, length of the body, or shape of the flea)

Click on image for a better view. Photos by M. Merchant.

If you guessed the flea on the left was my mystery flea, you'd be correct. But did you guess right for the right reason?

First, it wasn't the legs. Both fleas are "host fleas", which means they live most of their adult lives on a host. Host fleas must have strong jumping legs to gain access to this host. Nest fleas, on the other hand, live in the nests of their hosts (usually rodents or birds), only living on the host long enough to take a blood meal and returning to the nest after dinner. Nest fleas rely less on jumping and and more on crawling within the nest to feed, so the third pair of legs is more like the second pair in size.

The big difference between these two fleas is the presence or absence of dark, comb-like bristles on the face and behind the head. The cat flea has combs both above the mouth (called a genal comb) and on the tail-edge of the first thoracic segment (pronotal comb) behind the head. Fleas with both genal and pronotal combs are relatively rare, narrowing down their probable identity considerably. Most fleas found indoors with two combs like this in homes are either cat fleas, Ctenocephalides felis, or dog fleas, Ctenocephalides canis.

The flea on the left lacks both a genal and a pronotal comb, ruling out cat flea. This flea is a human flea, Pulex irritans. The human flea, like the cat flea, has many potential hosts including small mammals, canines, pigs, humans, and even burrowing owls.

Entomologists have identified over 2,500 different kinds of fleas from around the world. Most of these fleas are highly fussy about their food, feeding on the blood of only one or a few closely related kinds of hosts. These two fleas are exceptions. Besides cats, the cat flea gladly feeds on dogs, opossums, raccoons (two frequent wildlife hosts that can bring fleas into homes when pets are not present), foxes, skunks, cattle, rats and rabbits, to name a few. [Curiously, squirrels do not seem to be a listed host of cat fleas, so are not likely to be the source of fleas in homes with no cats or dogs.]

Why worry about flea identification? Because flea ID may provide clues to a possible source of a flea problem. If fleas found in a home or on a pet are not cat fleas, it's possible that the fleas are coming from rodents or other wildlife. For example, rat fleas may suggest a rat or mouse infestation. Rat fleas may pose greater risk for the homeowner from flea-borne illness such as murine typhus, or even (more rarely) plague, though the cat flea is not without its own risks. Cat fleas on opossums have been associated with increased cases of murine typhus in California and Texas and other areas. Cat scratch disease may also be carried by cat fleas.

The following key is provided by the Centers for Disease Control (reprinted in the Mallis Handbook of Pest Control) and can help you identify some of the more common fleas found in structures or on pets. Combs can usually be seen by the practiced eye with a good 10X handlens. If you want to see other features in this key, however, you'll need a microscope. A 12X magnification will show genal and pronotal combs; but 25X to 50X is needed to see smaller characters shown on the key.

If you do not see pronotal and genal combs on a flea collected in a home, and do not have a good microscope, it's best to save some specimens in either 70% ethanol or rubbing alcohol. Specimens can then be sent to an entomologist for positive identification. Five or more pointed teeth on both the genal and pronotal sites will narrow any flea found on a pet or in a building down to a cat or dog flea, both of which have similar host ranges and control measures.

Click on key for a better view.

Next time you get your hands on some fleas, take a closer look. Check for combs and use the key. I predict you'll get that same thrill of satisfaction entomologists get when being able to put a name on something that most people can barely see. Your customers will be impressed too.

Wednesday, February 12, 2020

It doesn't take a PhD to predict that termite season is likely to arrive early this year. Record warm temperatures and abundant rain are already stirring the pots of pest activity in Texas, so all pest control companies should be gearing up now for a busy and early year.

If your company is hiring new staff this spring, or needs to get existing technicians cross-trained for termite season, this class is for you. IPM House will be offering a one-day, 2020 Termite Training for New Technicians class on February 28. Dr. Bob Davis, BASF Corporation, and Kevin Keim of Corteva, will be assisting our team with an interactive course in termite biology and control.

If you've not yet attended an IPM Experience House course, this is a great opportunity to get involved. All IPM House classes are an interactive mix of both classroom and field training. The training day includes lecture and Q&A with top experts, microscope exercises and hands-on activities at the IPM House itself.

We especially welcome PMPs from other parts of Texas and out of state to attend and become part of the IPM Experience House alumni.

Thursday, January 23, 2020

For anyone who needs structural or ag CEU credits in the area of turf and ornamental pest management, 2020 Spring IPM Conference registration is now open.

This year's program will focus on how pesticides accomplish the challenging task of controlling pests. It's not as easy or as simple as you might think!

Dr. Christopher Bibbs with Central Life Sciences will talk on how insecticides work. Our Dallas turfgrass extension specialist, Dr. Chrissie Segars, will cover modes of action of herbicides. And Scott Smith, Bell Labs, will review rodents and how rodenticides work. In addition, Janet Hurley, our school IPM program specialist, will be providing the latest updates on what's going on with re-certification rules and pesticide regulations. And I will review those common, and not-so-common insects associated with turfgrass.

Our challenge every year is to make sure when you attend an IPM Conference, you leave with at least one useful piece of knowledge. There will be lots to learn at this meeting, so register now by going to https://agriliferegister.tamu.edu/IPM. As usual, a great lunch will be provided.

Thursday, January 16, 2020

A few years ago I was called to a home in the Dallas area to look at a stubborn "fire ant" problem. Indeed the numerous mounds did look much like fire ant mounds, and the red ants like fire ants; but closer inspection showed the ants to be pavement ants.

The name "pavement ant" comes from its preference for nesting in open, well-drained gravelly soil typical of sites under sidewalks and other pavement. By building roads and laying concrete throughout our cities it seems we have created the perfect habitat for these ants.

Temperate climates, like those of the Northern and Midwestern states, are especially favorable to pavement ants. In some states, pavement ants are the most common household ant, foraging for crumbs and swarming indoors like termites or carpenter ants. Though less common in Texas, I suspect pavement ants are more common than we realize, often being mistaken for fire ants.

According to BugGuide.net, there are seven native and introduced species of Tetramorium in the U.S. and 455 species worldwide. By far the most common and widespread species has, until recently, been referred to as Tetramorium caespitum or, more mysteriously, "Tetramorium species E". This is the only Tetramorium that is a common urban nuisance pest.

It's not common to have an important pest insect whose identity remains a mystery for almost 100 years since it was first recorded. It turns out that the genus to which pavements ants belong is a real "brier patch" of related and difficult-to-tell-apart species. Taxonomists who have studied the group have realized as much and out of frustration have been calling our pest pavement ant "species E" within the T. caespitum "brier patch". That has now changed.

Two recent papers clarified the identity of these common ants, and they required some ingenious sleuthing to do it. A paper by Herbert Wagner and colleagues used a combination of two kinds of DNA, numerous body features and ecological observations to untangle the briers obscuring the Tetramorium species in Europe. When they finished they (in a very scientific way) said "Phew!" and noted that it took six types of analysis to solve the "highly intricate" problem of identifying the European Tetramorium. Without both molecular (DNA) studies and studying the morphological features of the ants, they never would have solved the puzzle.

The new name of the American pest pavement ant is Tetramorium immigrans, an appropriate name since our pest turns out to be an immigrant from Europe. Very similar in appearance to the Tetramorium caespitum first described and named by Carl Linnaeus in 1758, a group of researchers based in Florida and led by Yuanmeng Zhang recently studied the genetics of Tetramorium immigrans populations in the U.S. In Zhang's study, molecular evidence was taken from 90 samples collected across the country by mostly school children using Pecan Sandies® cookie crumbs to attract the ants. The lack of genetic diversity among all the samples collected suggests strongly that all of today's ants came from a one-time introduction, perhaps as long as 200 years ago.

What's in a Name?

Why is knowing the name of an insect important? Because IPM is important. Integrated pest management is the definition of modern, effective pest control. One of the key principles of IPM is that control methods should be based on knowledge of the biology and behavior of the pest. Without knowing what pest you are facing, its impossible to know with any certainty the lives and behaviors (and weaknesses) of any pest.

Knowing the right species of ant will also help in selecting an appropriate bait. In the case of pavement ants, the Advion® Fire Ant Bait has a label that includes pavement ant. In the case of the Dallas home with fire ants, Advion® performed well against that infestation.

Recognizing Pavement Ants

Pavement ant. Note the two node segments between thorax and gaster, two
small spines toward the end of the thorax, and parallel grooves on
the head and body. Color ranges from light brown to black. From theAnt Identification Guide by Bayer Environmental Science.

So how do you recognize pavement ants? Determining Tetramorium ants to an exact species can be a challenge and requires a very fine microscope. Fortunately, the genus is not hard to identify with a hand lens or modest microscope. And most Tetramorium found in urban settings and as indoor pests in the U.S. will be T. immigrans.

Pavement ants are in the ant subfamily Myrmycinae. Like all myrmycines, pavement ants have stingers (rarely used) and two small nodes (bumps) between the thorax and gaster (tail segment). In addition, look for two small spines on the last segment of the thorax. Color may range from light brown to black, and all the workers from a given nest will be the same size (monomorphic). Pavement ants may superficially look like fire ants but they are generally slower, less aggressive when their mound is disturbed, and do not sting.

Knowing what kind of ant, or any insect, you have in hand is essential to everything we do in pest control. And having taxonomists working behind the scenes to figure out what pests we have is a real benefit to our industry.

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About Me

I have served as entomology specialist for Texas AgriLife Extension since 1989. I get to work with, and for, a bunch of great people including pest management professionals, school facilities managers, extension volunteers, researchers and other extension professionals. My areas of specialty center on research on insects affecting man including spiders, scorpions, fire ants, termites and others. My program also focuses on training school maintenance professionals in principles of integrated pest management (IPM). Our goal is to make schools healthier, cleaner places to study and live.